Effects of Insulation Residues on the Contacting Process of Copper Flat Wire Connections

Due to the increasing electromobilization, there is an interest in making electric drives in general as well as the production of electric vehicles more energy efficient and environmentally friendly. This is an important research focus of the Institute FAPS at the Friedrich-Alexander-Universitat Erlangen-Nürnberg (FAU). The results presented in this paper focus on the process step of stripping the enameled copper conductors. This is necessary in the contacting process because many contacting technologies, such as contacting by laser beam welding, require a residue-free stripped weld area. Otherwise, the burnt and remaining insulation material can cause undesirable welding spatter or lead to pore formation in the contact area. Insulation residues thus influence the formation of a strong and stable welded joint. With this background, the effects of insulation residues on flat wire joints are investigated in more detail in this paper. For this purpose, the fundamentals in the area of enameled copper wires, stripping and contacting are first explained. In the main part of the paper, different process for stripping as well as subsequent contacting of the used samples by laser welding are described. After the experiments have been carried out, the examination of the samples using various methods is discussed. The samples are examined optically, by metallographic sections, by electrical resistance measurements and by fluorescence measurements. The results are evaluated and compared and the suitability of the fluorescence measurement is discussed.